1. Field of the Invention
The present invention relates to a lead frame conveying apparatus and more particularly to a lead frame pushing mechanism which pushes lead frames into a storage magazine after a bonding has been done on the lead frames in, for example, wire bonding, die bonding, etc.
2. Prior Art
When lead frames are transferred by a conveyor to store them in a magazine, it is necessary to make sure that each lead frame is completely inside the magazine. Two types of devices are presently used to bring each lead frame into the magazine.
One type uses a storage magazine that is of a special structure, and a conveyor extends into this special storage magazine. Another type uses an ordinary shape storage magazine near the end of conveyor. In this device, the efficiency of the lead frames pushed into the storage magazine depends upon the relationship between the conveying force (or a propelling force) of the conveyor and the friction between the magazine and the lead frames. In order to obtain good entry efficiency of the lead frames, a pinch roller is used. The pinch roller which pushes each lead frame on the surface of the conveyor is installed near the end of the conveyor. The conveying or propelling force of the conveyor is, as a result, utilized to its maximum extent possible.
In the case of the device of first type as described above, the storage magazine of a special structure is used; accordingly, it lacks versatility. As a result, the device of the second type is generally used.
In the second type, there is a gap between the end of the conveyor and the storage magazine. Accordingly, unless the inertia of the lead frame created by the propelling force of the conveyor is utilized fully, the lead frame is not completely put in the storage magazine.
As described above, how smoothly the lead frames are pushed into the storage magazine depends on the relationship between the conveying force (propelling force) of the conveyor and the friction between the magazine and the lead frame, and it often occurs that the lead frames are not orderly stored in the magazine. In addition, the speed of the conveyor needs to be high in order to pass each lead frame across the gap. If, however, the speed of the conveyor is too high and the inertia of the lead frames is too strong, the lead frames can pass through the storage magazine and fly out on the opposite side. Accordingly, in order to avoid such flying out, a stopper is required. However, if a stopper is used, damage may occur when the lead frame hits the stopper. In other words, wires bonded to a lead frame may be removed or bent when the lead frame hits the stopper.